Nautical ice-breaking structures



July 21, 1970 s". E. ALEXANDER ,5

NAUTICAL ICE-BREAKING STRUCTURES Fi ed Au a. less United States Patent 3,521,591 NAUTICAL ICE-BREAKING STRUCTURES Scott E. Alexander, Ottawa, Ontario, Canada, assignor to Alexbow Canada Ltd., Calgary, Alberta, Canada Filed Aug. 6, 1968, Ser. No. 750,583 Claims priority, application Canada, Aug. 15, 1967, 997,885 Int. Cl. B6311 35/08 U.S. Cl. 114-41 8 Claims ABSTRACT OF THE DISCLOSURE A bow for a vessel for ice-breaking has a forwardly projecting forefoot extending under the ice, an upstanding blade that projects upwardly to a relatively sharp edge extending along the upper central region of the forefoot. Outwardly and rearwardly, there are surfaces shaped for elevating pieces of ice cut by the bow and for moving these pieces outwardly for stacking on pack ice beside the vessel.

This invention relates to improvements in nautical ice-breaking structures, that is to say structures designed for breaking naturally formed ice on the sea or in rivers and lakes by virtue of a relative movement between the ice and the breaking structure.

The principal application of the invention lies in the field of construction of bow structures for vessels, that is to say ships of all sizes from the largest ocean-going ships down through tugs and boats to small pleasure craft, such as motor boats and even canoes and the like.

In its applicability to the formation of bow structures for vessels the invention may be applied to the vessel itself, in the sense of being incorporated in the design of the vessels hull as originally built, or it may take the form of a separate device that is attached to the vessel. Such an attachment may be permanent, or at least semi-permanent, as by welding an entire bow assembly in front of the normal bow of the vessel--a method perhaps most likely to find favour in relation to relatively large ships that have already been built and which are later to be outfitted for ice-breaking duty, either permanently or for a single winter season. In the case of small vessels, pleasure craft for example, the bow assembly, although of essentially the same shape as in the case of an oceangoing ship, will be much smaller in scale and lighter in weight, so that it will become feasible to attach the ad ditional bow to the front of the vessel temporarily, when required, by convenient manually operated devices, such as screw clamps or the like. Another important form that a bow structure according to the present invention may take is as a free-floating device (a vessel in its own right) that is designed to be pushed by a powered vessel, for instance a tug. Such a device will contain buoyancy tanks to control its own waterline level substantially independently of the pushing vessel, although the extent to which relative movement between the two vessels is permitted in a seaway will depend on how tightly they are coupled together. It will be necessary to maintain linkage between the two vessels, in addition to the contacting surfaces through which the pushing force is transmitted.

The principal feature of novelty of the invention resides in the use of a narrow upstanding splitter blade mounted to extend along a central ridge defined by ice deflecting surfaces that extend rearwardly and upwardly away from a projecting nose (forefoot) formed by the leading edges of such surfaces. It has been discovered that, when this splitter blade encounters ice from the underside thereof, it produces a splitting action that has not previously been observed in ice breakers. .Due primarily, it is believed, to the relative sharpness of the 3,521,591 Patented July 21, 1970 upper edge of this blade, the ice is not appreciably lifted before it is split by the blade. This action provides separated pieces of ice for the deflecting surfaces to handle. This unusual action is more fully described below.

Other features and advantages of the invention are also discussed below.

Various embodiments of the present invention are illustrated diagrammatically in the accompanying drawings. It is to be understood that these illustrations and the following specific description relating thereto are provided by way of example only and not by way of limitation of the broad scope of the present invention, which scope is defined by the appended claims.

In the drawings:

FIG. 1 is a plan view of a free-floating bow structure incorporating the invention, taken on the line I--I in FIG. 2;

FIG. 2 is a side view of the structure of FIG. 1, taken on the line IIII therein; and

FIG. 3 is a rearward-looking section through the structure, taken on the line IIIIII in FIG. 2.

FIGS. 1 to 3 show a free-floating bow device 10 comprising a hollow tank portion 11, separate internal spaces in which can be filled with ballast water in the conventional manner and to the degree necessary to give the device the desired waterline level, attitude and general trim. This rear portion 11 includes a V slot 12 for receiving the bow of a pushing vessel (not shown) and a keel 13 to encourage straight running of the assembly. In practice, cables or other suitable linkages will be provided extending from lateral locations on the pushing vessel to corresponding lateral locations on a superstructure 14 of the device 10.

The ice-breaking and plowing forward portion 20 cornprises a pair of plow blade surfaces 21 turned over at their upper edges 22. Along the central forward line where the surfaces 21 come together to define a central ridge, there is provided a narrow upstanding splitter blade 23 that extends in a fore and aft direction, tapering down at its front 24 to form a sharply pointed nose 25 with the front edges of the blade surfaces 21, and merging at its rear 26 into the steeply climbing V edge 27 formed by the plow blade surfaces 21 at this location. A fiat bottom plate 28 is also provided. The portion of this structure below the normal waterline WL is referred to as the forefoot.

It is important to note that the blade 23 is generally untapered in form, except for its extreme front end 24 below the normal waterline WL, where it is tapered down for reasons of structural strength. It is similarly tapered at its extreme rear end 26 where like considerations apply. However the main central portion of the blade 23 is untapered, and is therefore essentially of uniform height throughout its length, at least in the critical areas in the vicinity of the typical waterline WL.

The splitter blade 23 will be sharp along its upper edge which may, for example, be formed of heavy steel plate.

Alternatively, the sharp edge may be formed by a strong bar secured along one edge of a steel plate. In this connection, it is to be appreciated that the term sharp is to be interpreted in the light of the function that is to be performed by the part in question and in the light of typical ship surfaces. While a A2" diameter rounded (i.e. semi-cylindrical) surface would hardly be considered sharp in the normal sense of the word, in comparison with the other surfaces of the device, it is effectively very sharp. Alternatively, the upper edge of the blade may be serrated or toothed.

Study of the performance of the arrangement shown in FIGS. 1 to 3 during actual test runs on firmly packed ice with a maximum of about 18" thickness on Lake Ontario has not only demonstrated the excellent icebreaking and ice-displacing properties of the arrangement, but has also revealed an unexpected and favourable action by the splitter blade 23. It was observed (and this fact has been confirmed by photographs) that the action of the blade 23 is essentially one of splitting the ice (in contrast to lifting), for which reason it is referred to as a splitter blade. Instead of breaking the ice sheet by lifting it in the middle (an action that takes place with a normal under-ice probe not fitted with a blade such as the blade 23, as evidenced by the presence of visible radial cracks), the present improved bow construction including essentially the sharp upstanding central blade extending therealong breaks the ice sheet immediately ahead of the blade 23 by an action which can be described as splitting (or perhaps shattering or crushing). Little or no lifting takes place until the main plow blade surfaces 21 come into contact with the ice and by this time the blade 23 has split the ice. While large lumps of ice will normally still remain unbroken for deflection by these surfaces 21 as the vessel proceeds, such lumps will have been separated from each other at least along the line extending forwardly of the centreline of the bow. As a result there will be no tendency for large unbroken sections of ice to lie across the bow, straddling it from side to side. This particular action which the present construction achieves is especially economical in usable power, and it has been found that the power needed to clear a channel through a given thickness of ice is significantly less with the present construction than with conventional ice-breaking bows that are designed to ride up on top of the ice and break it by downward pressure.

Moreover, the sloped plow surfaces 21 that are located beside and rearwardly of the blade 23 face outwardly and upwardly to deflect the broken ice to the outsides. The shape of these surfaces, including the turned over upper edges 22, tends to have the effect of piling up the broken ice onto the sheet ice at the edges of the channel being cut, thus helping to reduce the number of loose pieces of ice floating in the vessels wake and thus further improving the overall performance of the present bow construction.

The angle of blade divergence A (FIG. 1) will preferably be of the order of 30, but can go as high as 45, or as low as it is feasible to make it without causing the device to become excessively long. The angle of attack B will preferably lie within the range of to but may go as high as when the pushing vessel has plenty of power, or as low as 15 when less power is available and the attendant increased length of the device can be tolerated.

In order to achieve the above-described splitting action it is necessary that the splitter blade 23 should have substantially vertically extending flat sides projecting for a substantial height above the central ridge defined by the intersection of the two plow surfaces 21. This height will be related to the ice thickness to be broken, which thickness will in turn control the overall size of the bow construction and the power needed to drive it forward. In general terms, it can be said that the blade height should vary between about one third of the ice thickness for very thick ice, say six or more feet, up to about two thirds of the ice thickness for relatively thin ice, say eighteen inches or less, with a typical average ratio of blade height to ice thickness of the order of a half.

When the invention is embodied in a free-floating separate device in accordance with the form of the invention illustrated in the drawings, the maximum width of the bow will conveniently be made slightly greater than that of the pushing vessel (usually a tug). This facilitates the tug travelling or turning in the slightly larger channel cut by the bow and avoids any tendency for the pushing vessel to jam against the sides of the ice.

When the bow construction is fixedly incorporated into the hull line of the powered vessel itself, either permanently or temporarily, the bow may be as wide as or even slightly wider than the vessel, when the latter is not very large. When it is large, however, further merging sloping surfaces will normally be provided to act as continuations of the deflecting plow surfaces of the bow in order to lead ice all the way outwardly beyond the sides of the vessel and pile it onto the ice at the sides of the channel.

In the case of very small boats that would only attempt to cut a channel for themselves through an inch or two of ice, the question of deflection of the broken ice becomes of relatively little importance. The essential requirement is a structure similar to the right hand part of the device 10 shown in FIG. 1 with suitable conventional manually adjustable fittings for securing the bow to the front of the boat.

Since these various modifications do not deviate from the essential structure shown in FIGS. 1 to 3, no separate illustration thereof has been considered necessary.

I claim:

1. A bow construction for a vessel for use in ice breaking, comprising upwardly sloping surfaces converging to define a central ridge extending forwardly and downwardly to terminate in a forwardly projecting forefoot located below the waterline for insertion beneath a surface layer of ice, said forefoot being pointed in side profile and having a plan profile diverging from a pointed tip more rapidly than said side profile whereby at the waterline the forefoot is substantially greater in breadth than in height; on each side of said ridge, upwardly and outwardly facing deflecting surfaces extending rearwardly from the forefoot and transversely outwardly from said ridge for deflecting ice in an outward and generally upward direction as the bow moves forward; and, extending along said ridge, a narrow upstanding splitter blade for splitting the ice forward of said deflecting surfaces, said splitter blade having substantially vertically extending flat sides projecting above said ridge to define a top edge that extends substantially parallel with said ridge at least in the longitudinally central, ice-splitting portion of said blade located in the vicinity of the waterline.

2. A bow construction according to claim 1, wherein said forefoot has a plan profile diverging along substantially straight edges from said pointed tip, such edges enclosing an angle of about 60.

3. A bow construction according to claim 1, wherein the forefoot is essentially fiat bottomed.

4. A bow construction according to claim 1, wherein said splitter blade has an angle of attack to the horizontal of approximately 30.

5. A bow construction according to claim 1, wherein said deflecting surfaces have an angle of blade divergence to the splitter blade within the range of approximately 20 to approximately 35.

6. A bow construction according to claim 1, wherein said deflecting surfaces include turned over, downwardly facing, upper portions for projecting deflected ice downwardly onto ice edges extending along the sides of a channel being cut.

7. A bow construction according to claim 1, wherein the height to which said splitter blade sides project above said ridge is substantially uniform along its effective length and said height lies within the range of approximately one third to approximately two thirds of the thickness of ice that the bow is constructed to break.

8. A bow construction according to claim 7, wherein said height is in the vicinity of the lower value of said range when said thickness is large and in the vicinity of the upper value of said range when said thickness is small.

References Cited UNITED STATES PATENTS 151,774 6/1874 Grant 11441 993,440 5/1911 Duplessis 114-41 812,656 2/1906 lulhe 114-63 TRYGVE, M. BLIX, Primary Examiner 

